The present invention relates to motor control systems, and in particular, to a motor control system providing a convenient backplane for interconnecting motor control modules.
Multi-axis motor controllers are used in industrial automation and manufacturing systems such as conveyer lines and multi-axis machine tools which require coordinated control of multiple motors. Generally, these systems include a main control module coupled to an axis control module for each motor of the system. The main control module is programmable to provide independent control of the system or may receive external commands over a high-speed communication link from a programmable logic controller (PLC) or the like. The main control module provides power and command signals to the individual axis control modules which process the power and, according to the command signals, provide drive signals to the associated motors. Feedback signals from the motors may be received by the axis control modules to provide more sophisticated feedback control of the motors and may be communicated to the main control module.
The number of axis control modules may be varied to allow the motor control system to be flexibly configured to applications requiring different numbers of motors. The main control module and the axis control modules are typically mounted adjacent to each other with their rear faces attached to a panel. Data signals (for example, command signals) may be exchanged between the main control module and the axis control modules (collectively “motor control modules”) on ribbon cables or on a backplane having a number of parallel conductors carried on a printed circuit board supporting electrical connectors attaching to corresponding connectors on the motor control modules.
The power necessary to drive the motors is normally provided by separate connections between the motor control modules either using large-gauge point-to-point wiring or metal bus bars extending between the modules, typically connecting along the top or from sides of the modules with screw fasteners. The wires or bars and their connection points must be properly insulated to protect users against the high voltages typically employed. Connecting and disconnecting the motor control modules from power is time consuming.
An improved interconnection system for motor control modules is described in U.S. Pat. No. 5,493,194 entitled “Control Signal and Power Bus Connector Arrangement for a Multi-Axis Motor Control” assigned to the same assignee as the present invention and hereby incorporated by reference. In this system, parallel conductor segments are built into the front of each motor control module. Each conductor segment includes connectors on its right and left sides so that it may be joined to other connector segments on adjacent motor control modules. As the motor control modules are assembled, their connector segments are joined creating a path of power and data communication between the motor control modules. The conductor segments incorporate electrical shielding and may slide laterally along the face of their respective motor control modules, to a limited degree, to allow motor control modules to be individually engaged and disengaged with other motor control modules after the motor control modules are mounted to the panel.
This approach provides a number of advantages including the ability to rapidly connect and disconnect multiple motor control modules and the ability to easily connect different numbers of motor control modules. Nevertheless, one disadvantage to this approach is that the depth (from rear to front face) of each motor control module must be similar so that the connector segments align and can be engaged. This requirement limits flexibility in designing smaller motor control modules that take advantage of reductions in electrical component size and/or interconnecting motor control modules of different generations having different form factors.